CN102661243A - Forecast correction pitch variation control method for doubly-fed induction wind power generator set - Google Patents

Abstract

The invention provides a forecast correction pitch variation control method for a doubly-fed induction wind power generator set, and belongs to the technical field of fan pitch variation control. The method comprises the following steps of: preprocessing wind speed; determining a forecast value of a pitch angle beta; and performing deviation correction on the forecast value of the pitch angle beta. The practicability is high; the wind energy conversion efficiency of the wind power generator set at low wind speed can be improved, and the wind power generator set can be effectively controlled to run without exceeding the speed limit at high wind speed; the wind power generator set can run safely and stably; the economic cost is low; and the method is suitable for pitch variation control systems of doubly-fed induction wind power generator sets at different power levels.

Description

Pitch control method is proofreaied and correct in a kind of forecast of double-fed induction wind-powered electricity generation unit

Technical field

The invention belongs to blower variable-pitch control technique field, pitch control method is proofreaied and correct in the forecast that specifically relates to a kind of double-fed induction wind-powered electricity generation unit.

Background technique

Wind-powered electricity generation has obtained developing rapidly in countries in the world as one of the most ripe clean energy resource of technology.Along with the development of wind generating technology, variable speed constant frequency wind-powered electricity generation unit has become the mainstream model of grid type wind-power electricity generation.Because the randomness and the uncertainty of wind energy, wind-driven generator are difficult to stabilize because wind speed changes the power swing that causes through self regulating, and are that it is more obvious that this point embodies when wind speed surpasses rated wind speed particularly.

Variable blade control system realizes that through the propeller pitch angle of regulating wind energy conversion system the power output of smooth wind power unit improves the fan operation performance to the making full use of of wind energy.Compare with the fixed pitch wind power generating set; The pitch-controlled wind-driven generator group has at rated power puts above stable output power; Equal-wattage unit rated wind speed is low, do not receive such environmental effects such as current density variation and advantage such as good startup and braking ability; Therefore, speed-changing oar-changing consists of the mainstream model of Large-scale Wind Turbines research and development and application apart from wind-driven generator.

At present, the measured value of the active power that traditional change oar control PI or the PID regulative modes of adopting, input signal send for the wind-powered electricity generation unit more and draws error signal after the peak output reference value is compared, and input PI controller produces propeller pitch angle controlling value β _Ref, the propeller pitch angle with reality compares again, and the propeller pitch angle error signal is input to the servomechanism of propeller pitch angle control system, specifically controls as shown in Figure 1.Wind power control system is in the variable blade control system that adopts the PI control mode; Can be implemented in below the rated wind speed; The control propeller pitch angle is realized maximal wind-energy capture, more than rated wind speed, and the output of the control propeller pitch angle restriction wind-powered electricity generation power of the assembling unit; Protection wind-powered electricity generation unit nonoverload avoids the wind-powered electricity generation unit mechanical failure to occur.But the traditional PI control system is a kind of linearity control mode; And that blower fan control system has is very strong non-linear; Therefore need in modeling process, carry out linearization process to system, choosing system modelling of linearization operation point is most important, and choosing of different operating point affects the PI parameter tuning; If it is incorrect that the PI Control Parameter is adjusted, then can't accurately control the complex nonlinear variable blade control system.

Simultaneously; Because the existence of RANDOM WIND variable will cause the irregular variation of wind speed in the actual wind speed; Particularly near rated wind speed, because the influence that frequent fluctuation possibly produce two aspects: (1) variable blade control system continuously influences the wind turbine output performance to the adjusting repeatedly of propeller pitch angle; (2) variable blade control system is machinery control, and system response time is longer, and the wind speed acute variation will cause control system can't in time respond current wind speed variation, produce control deviation.

Along with the continuous development of control technique, advanced control techniques such as fuzzy control, ANN Control are constantly introduced in the variable blade control system, improve the control accuracy of complex nonlinear pitch-controlled system.Based on the change oar control technique of fuzzy PI hybrid control is the control system that control experience and knowledge with operator or expert is expressed as going to control with the control law of language variable description controlled device.The Fuzzy control system controlling object is the complex nonlinear pitch-controlled system; Be difficult to set up precise math model; The method of controlling these objects simultaneously is not to be present in these knowledge sources with certain ready-made form to choose from, but derives from the expert or the operator's in this field knowledge and experience.Therefore, fuzzy rule set up the dependence design experiences, lack of uniform standard, and algorithm relative complex, practicability is not strong.

Adopt fuzzy control to realize maximum power tracing MPPT (Maximum Power Point Tracking); Can not require the mathematical models of knowing controlled device; Only correlation experience knowledge and operating data need be provided; Be applicable to that solving classical control system insoluble non-linear, time becomes and delay system, but there is static error problem bigger than normal in this control mode.

Summary of the invention

In order to overcome the deficiency of above-mentioned existing technology; The present invention provides a kind of forecast of double-fed induction wind-powered electricity generation unit to proofread and correct pitch control method, and is practical, both can improve the wind energy conversion efficiency of wind power generating set when hanging down wind speed; Can effectively control wind power generating set not overspeed when high wind speed again; Guarantee the wind power generating set safe and stable operation, financial cost is low, is applicable to the variable blade control system of the double fed induction generators group of different capacity grade.

In order to realize the foregoing invention purpose, the present invention takes following technological scheme:

Pitch control method is proofreaied and correct in a kind of forecast of double-fed induction wind-powered electricity generation unit, and said controlling method may further comprise the steps:

Step 1: pretreatment wind speed;

Step 2: confirm propeller pitch angle β predicted value;

Step 3: the said propeller pitch angle β of drift correction predicted value.

In the said step 1, wind speed is carried out pretreatment according to the randomness employing moving average method of wind speed.

It is following that moving average method is carried out pretreated process to wind speed:

If { ε _tBe irregular RANDOM WIND sequence, { ε _tIndependent to time t, mathematical expectation E (ε _t)=0, mean square deviation

σ then ²(ε _t)=E ²(ε _t), ε _tN item rolling average sequence { ε _t ^(l)Be:

${{\mathrm{\ϵ}}_t}^{\left(l\right)}=\frac{1}{N}({\mathrm{\ϵ}}_t+{\mathrm{\ϵ}}_{t+1}+...+{\mathrm{\ϵ}}_{t+N-1})---\left(1\right)$

Then the covariance of the variance and the s item of being separated by is respectively:

$D\left({\mathrm{\ϵ}}_t\right)={\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_t}^{\left(l\right)}\right)=\frac{1}{N}{\mathrm{\σ}}^2---\left(2\right)$

$\mathrm{cov}({{\mathrm{\ϵ}}_t}^{\left(l\right)},{{\mathrm{\ϵ}}_{t+s}}^{\left(l\right)})=\left\{\begin{array}{cc}\frac{1}{N^2}\left[(N-s){\mathrm{\σ}}^2\right]& (N>s)\\ 0& (N\≤s)\end{array}\right.---\left(3\right)$

Can get by formula (2): ${\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_t}^{\left(l\right)}\right)={\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_{t+s}}^{\left(l\right)}\right)=\frac{1}{N}{\mathrm{\σ}}^2---\left(4\right)$

So, sequence { ε _t ^(l)S item correlation coefficient ρ _{T, t+s}For:

${\mathrm{\ρ}}_{t,t+s}=\left\{\begin{array}{cc}\frac{N-s}{N}& (N>s)\\ 0& (N\≤s)\end{array}\right.---\left(5\right)$

Can know sequence { ε by formula (5) _t ^(l)Adjacent s item have positive correlation coefficient, promptly original incoherent random sequence { ε _tHave positive correlation through after the rolling average, and make the random fluctuation sequence of non-rule become smooth fluctuation sequence.

In step 2, wind speed is got optimum propeller pitch angle β during less than rated wind speed _OptAs becoming oar control propeller pitch angle predicted value, said optimum propeller pitch angle β _OptObtain through the foline momentum method.

In step 2, wind speed obtains the propeller pitch angle predicted value under the current air speed value through the Newton interpolation during greater than rated wind speed.

In step 2, confirm propeller pitch angle β predicted value through following arbitrary method, wherein:

When 2-1) wind speed was less than rated wind speed, there was different optimum propeller pitch angle β in different wind _Opt, can know the mechanical output P that wind turbine produces according to aerodynamic principle _TurFor:

$P_{\mathrm{tur}}=\frac{1}{2}\mathrm{\ρ\π}{R}^2{C}_p(\mathrm{\λ},\mathrm{\β})V_W^3---\left(6\right)$

In the formula (6): ρ is an air density, and R is the wind wheel radius, V _WFor driving the effective wind speed of wind turbine, tip speed ratio λ=w _TurR/V _W, w _TurBe wind speed round, C _pBe the wind wheel utilization factor, according to the function C of curve fitting _pFor:

$\left\{\begin{array}{c}{C}_p(\mathrm{\λ},\mathrm{\β})=0.22(\frac{116}{{\mathrm{\λ}}_i}-0.4\mathrm{\β}-5.0)e^{\frac{-12.5}{{\mathrm{\λ}}_i}}\\ {\mathrm{\λ}}_i=\frac{1}{\frac{1}{\mathrm{\λ}+0.08\mathrm{\β}}-\frac{0.035}{{\mathrm{\β}}^2+1}}\end{array}\right.---\left(7\right)$

When 2-2) wind speed is greater than rated wind speed, the permanent rotating speed operation of wind-driven generator this moment, the wind-driven generator output power is a rated power; Wind turbine rotating speed and output power are can the knowledge amount, simultaneously, because wind turbine blade radius is a definite value; Air density can be considered constant; Then variable blade control system will change and move with wind speed, and the propeller pitch angle output value can be determined by wind speed

Adopt Newton interpolation method match wind speed-propeller pitch angle change curve, n the Newton interpolation polynomial that is calculated wind speed-propeller pitch angle by formula (6), (7) is:

β′ _n(V _W)＝β[V _W0]+β[V _W0，V _W1](V _W-V _W0)+β[V _W0，V _W1，V _W2](V _W-V _W0)(V _W-V _W1)+…

+β[V _W0，V _W1，…，V _Wn](V _W-V _W0)(V _W-V _W1)…(V _W-V _W（n-1）)(9)

In the formula: β [V _W0, V _W1..., V _Wn] be n the n jump quotient that the corresponding propeller pitch angles of different wind speed calculate, by the pairing propeller pitch angle value of different wind speed β [V _W0], β [V _W1] ..., β [V _Wn] calculate:

In the said step 3, the step of the said propeller pitch angle β of drift correction predicted value is following:

3-1) input signal is wattful power messurement value and the rotating speed deviate that wind-driven generator sends, and obtains the propeller pitch angle reference value through PI control;

3-2) the propeller pitch angle reference value compares with actual propeller pitch angle, obtains servomechanism installation and servo ratio FACTOR P that the propeller pitch angle error signal is input to pitch control system _PitchMultiply each other.

Said servomechanism installation is set to 0 ° and 27 ° respectively with propeller pitch angle β upper lower limit value, so that the safe and stable operation of said pitch control system.

Compared with prior art, beneficial effect of the present invention is:

1. this method is applicable to the variable blade control system of the double fed induction generators group of different capacity grade;

2. based on the randomness and the polytropy of wind speed; At first the wind speed that drives wind turbine is carried out preliminary treatment; Utilize the method for moving average that the incoherent RANDOM WIND sequence of script is had positive correlation after rolling average; Make the random fluctuation of non-rule become smooth fluctuation, effectively reduce unnecessary change oar action, improve the stability of variable blade control system;

3. respectively to quick given propeller pitch angle predicted value under low wind speed and two kinds of situation of high wind speed.When hanging down wind speed, the propeller pitch angle predicted value is set at the optimum propeller pitch angle β that utilizes the foline momentum method to calculate _Opt, improve the wind turbine control performance, improve the output power of wind turbine; When high wind speed, adopt the Newton interpolation method to obtain the propeller pitch angle predicted value under the current air speed value fast.This method significantly shortens the pitch-controlled system response time, effectively avoids traditional variable blade control system because the parameter tuning inaccuracy causes the system overshoot phenomenon;

4. be provided with correction link, revise the curve fitting error that causes owing to data interpolating in the prediction link, further improve and become the oar control accuracy;

5. this method financial cost is low, practical, both can improve the wind energy conversion efficiency of wind power generating set when hanging down wind speed, can effectively control wind power generating set not overspeed when high wind speed again, guarantees the wind power generating set safe and stable operation.

Description of drawings

Fig. 1 is traditional pitch control method schematic representation;

Fig. 2 is a pitch control method schematic representation of the present invention;

Fig. 3 is wind speed rolling average control implementation procedure schematic representation;

Fig. 4 is classical optimal power plotted curve;

Fig. 5 is wind speed-propeller pitch angle curve synoptic diagram;

Fig. 6 is certain model 2.0MW double-fed induction wind-powered electricity generation unit control structure schematic representation;

Fig. 7 is traditional pitch control method and a pitch control method wind speed correlation curve of the present invention in the instance one;

Fig. 8 is traditional pitch control method and a pitch control method active power correlation curve of the present invention in the instance one;

Fig. 9 is traditional pitch control method and a pitch control method propeller pitch angle correlation curve of the present invention in the instance one;

Figure 10 is traditional pitch control method and a pitch control method wind speed correlation curve of the present invention in the instance two;

Figure 11 is traditional pitch control method and a pitch control method active power correlation curve of the present invention in the instance two;

Figure 12 is traditional pitch control method and a pitch control method propeller pitch angle correlation curve of the present invention in the instance two;

Figure 13 is traditional pitch control method and a pitch control method rotating speed correlation curve of the present invention in the instance two;

Figure 14 is traditional pitch control method and a pitch control method wind speed correlation curve of the present invention in the instance three;

Figure 15 is traditional pitch control method and a pitch control method active power correlation curve of the present invention in the instance three;

Figure 16 is traditional pitch control method and a pitch control method propeller pitch angle correlation curve of the present invention in the instance three;

Figure 17 is traditional pitch control method and a pitch control method rotating speed correlation curve of the present invention in the instance three;

Figure 18 is traditional pitch control method and a pitch control method wind speed correlation curve of the present invention in the instance four;

Figure 19 is traditional pitch control method and a pitch control method active power correlation curve of the present invention in the instance four;

Figure 20 is traditional pitch control method and a pitch control method propeller pitch angle correlation curve of the present invention in the instance four;

Figure 21 is traditional pitch control method and a pitch control method rotating speed correlation curve of the present invention in the instance four.

Embodiment

Below in conjunction with accompanying drawing the present invention is done further explain.

Like Fig. 2, pitch control method is proofreaied and correct in a kind of forecast of double-fed induction wind-powered electricity generation unit, and controlling method may further comprise the steps:

Step 1: pretreatment wind speed;

Step 2: confirm propeller pitch angle β predicted value;

Step 3: the said propeller pitch angle β of drift correction predicted value.

In the said step 1, wind speed is carried out pretreatment according to the randomness employing moving average method of wind speed.

It is following that moving average method is carried out pretreated process to wind speed:

Like Fig. 3, establish { ε _tBe irregular RANDOM WIND sequence, { ε _tIndependent to time t, mathematical expectation E (ε _t)=0, mean square deviation σ then ²(ε _t)=E ²(ε _t), ε _tN item rolling average sequence { ε _t ^(l)Be:

${{\mathrm{\ϵ}}_t}^{\left(l\right)}=\frac{1}{N}({\mathrm{\ϵ}}_t+{\mathrm{\ϵ}}_{t+1}+...+{\mathrm{\ϵ}}_{t+N-1})---\left(1\right)$

Then the covariance of the variance and the s item of being separated by is respectively:

$D\left({\mathrm{\ϵ}}_t\right)={\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_t}^{\left(l\right)}\right)=\frac{1}{N}{\mathrm{\σ}}^2---\left(2\right)$

$\mathrm{cov}({{\mathrm{\ϵ}}_t}^{\left(l\right)},{{\mathrm{\ϵ}}_{t+s}}^{\left(l\right)})=\left\{\begin{array}{cc}\frac{1}{N^2}\left[(N-s){\mathrm{\σ}}^2\right]& (N>s)\\ 0& (N\≤s)\end{array}\right.---\left(3\right)$

Can get by formula (2): ${\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_t}^{\left(l\right)}\right)={\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_{t+s}}^{\left(l\right)}\right)=\frac{1}{N}{\mathrm{\σ}}^2---\left(4\right)$

So, sequence { ε _t ^(l)S item correlation coefficient ρ _{T, t+s}For:

${\mathrm{\ρ}}_{t,t+s}=\left\{\begin{array}{cc}\frac{N-s}{N}& (N>s)\\ 0& (N\≤s)\end{array}\right.---\left(5\right)$

Can know sequence { ε by formula (5) _t ^(l)Adjacent s item have positive correlation coefficient, promptly original incoherent random sequence { ε _tHave positive correlation through after the rolling average, and make the random fluctuation sequence of non-rule become smooth fluctuation sequence.

In step 2, wind speed is got optimum propeller pitch angle β during less than rated wind speed _OptAs becoming oar control propeller pitch angle predicted value, said optimum propeller pitch angle β _OptObtain through the foline momentum method.

In step 2, wind speed obtains the propeller pitch angle predicted value under the current air speed value through the Newton interpolation during greater than rated wind speed.

In step 2, confirm propeller pitch angle β predicted value through following arbitrary method, wherein:

When 2-1) wind speed was less than rated wind speed, there was different optimum propeller pitch angle β in different wind _Opt, can know the mechanical output P that wind turbine produces according to aerodynamic principle _TurFor:

$P_{\mathrm{tur}}=\frac{1}{2}\mathrm{\ρ\π}{R}^2{C}_p(\mathrm{\λ},\mathrm{\β})V_W^3---\left(6\right)$

In the formula (6): ρ is an air density, and R is the wind wheel radius, V _WFor driving the effective wind speed of wind turbine, tip speed ratio λ=w _TurR/V _W, w _TurBe wind speed round, C _pBe the wind wheel utilization factor, according to the function C of curve fitting _pFor:

$\left\{\begin{array}{c}{C}_p(\mathrm{\λ},\mathrm{\β})=0.22(\frac{116}{{\mathrm{\λ}}_i}-0.4\mathrm{\β}-5.0)e^{\frac{-12.5}{{\mathrm{\λ}}_i}}\\ {\mathrm{\λ}}_i=\frac{1}{\frac{1}{\mathrm{\λ}+0.08\mathrm{\β}}-\frac{0.035}{{\mathrm{\β}}^2+1}}\end{array}\right.---\left(7\right)$

When 2-2) wind speed is greater than rated wind speed, in conjunction with the classical optimal power plotted curve of Fig. 4 and formula (6) and (7) knowledge, the permanent rotating speed operation of wind-driven generator this moment; The wind-driven generator output power is a rated power, and wind turbine rotating speed and output power are can the knowledge amount, simultaneously; Because wind turbine blade radius is definite value, air density can be considered constant, and then variable blade control system will change and moves with wind speed; The propeller pitch angle output value can be determined by wind speed, by formula (6) and (7) must tip speed ratio-propeller pitch angle relation be:

$0.4\mathrm{\β}=\frac{116}{{\mathrm{\λ}}_i}-C-\frac{{\mathrm{K\λ}}^3}{e^{-\frac{12.5}{{\mathrm{\λ}}_i}}}---\left(8\right)$

In the formula: K is for to be calculated by wind turbine mechanical output, blade radius and control of density, and

C is a constant.

Because formula (8) is a complex nonlinear high order exponential function; Be not suitable for actual control system; Therefore, adopt Newton interpolation method match wind speed-propeller pitch angle change curve, n the Newton interpolation polynomial that is calculated wind speed-propeller pitch angle by formula (6), (7) is:

β′ _n(V _W)＝β[V _W0]+β[V _W0，V _W1](V _W-V _W0)+β[V _W0，V _W1，V _W2](V _W-V _W0)(V _W-V _W1)+…

+β[V _W0，V _W1，…，V _Wn](V _W-V _W0)(V _W-V _W1)…(V _W-V _W(n-1)) (9)

In the formula: β [V _W0, V _W1..., V _Wn] be n the n jump quotient that the corresponding propeller pitch angles of different wind speed calculate, by the pairing propeller pitch angle value of different wind speed β [V _W0], β [VW ₁] ..., β [V _Wn] calculate:

Calculation of wind speed is 12m/s respectively, 14m/s, and 16m/s, the propeller pitch angle value during 18m/s, utilize formula (9), (10) to obtain 3 Newton interpolation polynomials of wind speed-propeller pitch angle: ${\mathrm{\β}}_3^{\′}\left(V_w\right)=0.04754V_w^3-2.2200V_w^2-35.9958V_w-$ $190.6109---\left(11\right)$

Wind speed-propeller pitch angle curve by formula (11) match obtains is as shown in Figure 5.

The propeller pitch angle predicted value that the improvement pitch control method is taken all factors into consideration under low wind speed and the high wind speed condition is confirmed method; When hanging down wind speed; Get optimum propeller pitch angle as becoming oar control propeller pitch angle predicted value; When wind speed is higher than rated wind speed, adopt the Newton interpolation to obtain the propeller pitch angle predicted value under the current air speed value according to wind speed shown in Figure 4-propeller pitch angle curve.

The step of the said propeller pitch angle β of drift correction predicted value is following:

3-1) run on more than the rated wind speed when wind-power generating system; According to becoming the speed of response that propeller pitch angle reference value that the oar predictive control obtains can improve variable blade control system; But; Because the propeller pitch angle that forecasting model adopts curve-fitting method to obtain is to be obtained through interpolation method by the discrete pairing propeller pitch angle of air speed value, interpolation point be chosen at the precision of influence curve match to a certain extent; Therefore, the present invention is becoming the correction control that has added on the oar predictive control basis based on the PI controller, and input signal is wattful power messurement value and the rotating speed deviate that wind-driven generator sends, and obtains the propeller pitch angle reference value through PI control;

3-2) the propeller pitch angle reference value compares with actual propeller pitch angle, obtains servomechanism installation and servo ratio FACTOR P that the propeller pitch angle error signal is input to pitch control system _PitchMultiply each other; P _PitchBe used to limit the gradient that propeller pitch angle changes, whether the setting of this parameter rationally will directly influence the correct operation that becomes the oar link, if P _PitchExcessive, propeller pitch angle then can occur and be changed to threshold limit value suddenly by optimum propeller pitch angle, the blower fan output power is occurred than great fluctuation process.

Said servomechanism installation is set to 0 ° and 27 ° respectively with propeller pitch angle β upper lower limit value, so that the safe and stable operation of said pitch control system.

Selecting certain model rated capacity is that 2MW double-fed induction wind-powered electricity generation unit becomes oar control emulation contrast.Utilize DIgSILENT/PowerFactory emulation platform building double-fed fan motor unit control system, control structure is as shown in Figure 6, and rated wind speed is 11m/s, and the initially meritorious setting value of emulation trend is 2MW.

Instance one:

In the above wind speed model of rated wind speed, add the RANDOM WIND variable, the contrast simulation wind speed is not handled and wind speed equalization fan operation curve, and simulation result is shown in Fig. 7-9.Know that by Fig. 7-9 after the employing wind speed rolling average pretreatment, the wind speed of input control system of wind turbines becomes level and smooth; The propeller pitch angle operating frequency obviously reduces; The fluctuation of wind-driven generator active power of output reduces, because in the actual fan operation process, RANDOM WIND exists all the time; Can know through contrast simulation, adopt the wind speed pretreatment can effectively improve the blower fan access point quality of power supply.

Instance two:

It is 8m/s that basic wind speed is set in emulation, and the fitful wind maximum value is made as 3m/s, and zero-time is 10s, and fitful wind is kept 60s, and simulation result is shown in Figure 10-13.Can know by Figure 10-13; When wind speed during less than rated wind speed, it is 0 ° that variable blade control system is kept optimum propeller pitch angle, and cube increases the wind-driven generator output power along with the increase of wind speed; When wind speed during near rated wind speed; Allow propeller pitch angle to move in advance, mechanical failure occurs because of overload to prevent wind-powered electricity generation unit mechanical structure, but this moment rotation speed of fan still in the blower fan system allowed band; It is constant that improved pitch control method is kept optimum propeller pitch angle, and the wind-driven generator output power is higher than the output power under traditional pitch control method.Contrasting two groups of simulation results can know, when wind speed was lower than rated wind speed, improved pitch control method can make wind-driven generator export more active power in the rotating speed allowed band, improves the output characteristics of wind-driven generator.

Instance three:

It is 11m/s that basic wind speed is set in emulation, and the fitful wind maximum value is made as 4m/s, and zero-time is 10s, and fitful wind is kept 60s, and simulation result is shown in Figure 14-17.Can know that by Figure 14-17 when wind speed exceeded rated wind speed, two kinds of resulting propeller pitch angles of pitch control method all increased along with the increase of wind speed, not exceed its rated power through changing propeller pitch angle restriction wind-powered electricity generation unit mechanical output.Contrasting two groups of simulation results can know; The more traditional pitch control method action of improved pitch control method is faster; Can be more effectively wind-driven generator active power be maintained near the rated power; And can limit the wind-driven generator rotating speed better near setting value, prevent wind-driven generator long-time overspeed causing wind-driven generator mechanical failure, guarantee the wind-driven generator safe and stable operation.

Instance four:

It is 8m/s that basic wind speed is set in emulation, and when t=20s, wind speed is mutated into 15m/s, contrasts different pitch control method results shown in Figure 18-21.Can know by Figure 18-21; Be mutated into more than the rated wind speed below at wind speed suddenly by rated wind speed; All move at two kinds of pitch control method angles, and contrasting two groups of simulation results can know, improved pitch control method moment of wind speed sudden change because the more traditional pitch-controlled system of variable blade control system action is faster; Thereby the rising of wind-driven generator active power is mild relatively; The wind-driven generator operation is more stable, can make wind-driven generator comparatively fast get into the steady-state operation state from Figure 10 (b) though can know the traditional PI pitch control method, and its stable operation active power has surpassed the specified active power of system; And wind-driven generator machine rotating speed also is in long-time overspeed state; Though improved pitch control method is gone into stable operation than slow-motion, its power rise mild and can the meritorious output of fine restriction wind-driven generator near rated power and wind-driven generator rotating speed also are controlled at setting value well, hence one can see that; When wind speed suddenlyd change, improved pitch control method can be protected the not overpower operation of wind-powered electricity generation unit better.

Should be noted that at last: above embodiment is only in order to technological scheme of the present invention to be described but not to its restriction; Although the present invention has been carried out detailed explanation with reference to the foregoing description; Under the those of ordinary skill in field be to be understood that: still can specific embodiments of the invention make amendment or be equal to replacement; And do not break away from any modification of spirit and scope of the invention or be equal to replacement, it all should be encompassed in the middle of the claim scope of the present invention.

Claims (8)

1. pitch control method is proofreaied and correct in the forecast of a double-fed induction wind-powered electricity generation unit, and it is characterized in that: said controlling method may further comprise the steps:

Step 1: pretreatment wind speed;

Step 2: confirm propeller pitch angle β predicted value;

Step 3: the said propeller pitch angle β of drift correction predicted value.

2. pitch control method is proofreaied and correct in the forecast of double-fed induction wind-powered electricity generation unit according to claim 1, it is characterized in that: in the said step 1, according to the randomness employing moving average method of wind speed wind speed is carried out pretreatment.

3. pitch control method is proofreaied and correct in the forecast of double-fed induction wind-powered electricity generation unit according to claim 2, it is characterized in that: it is following that moving average method is carried out pretreated process to wind speed:

If { ε _tBe irregular RANDOM WIND sequence, { ε _tIndependent to time t, mathematical expectation E (ε _t)=0, mean square deviation σ then ²(ε _t)=E ²(ε _t), ε _tN item rolling average sequence { ε _t ^(l)Be:

${{\mathrm{\ϵ}}_t}^{\left(l\right)}=\frac{1}{N}({\mathrm{\ϵ}}_t+{\mathrm{\ϵ}}_{t+1}+...+{\mathrm{\ϵ}}_{t+N-1})---\left(1\right)$

Then the covariance of the variance and the s item of being separated by is respectively:

$D\left({\mathrm{\ϵ}}_t\right)={\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_t}^{\left(l\right)}\right)=\frac{1}{N}{\mathrm{\σ}}^2---\left(2\right)$

$\mathrm{cov}({{\mathrm{\ϵ}}_t}^{\left(l\right)},{{\mathrm{\ϵ}}_{t+s}}^{\left(l\right)})=\left\{\begin{array}{cc}\frac{1}{N^2}\left[(N-s){\mathrm{\σ}}^2\right]& (N>s)\\ 0& (N\≤s)\end{array}\right.---\left(3\right)$

Can get by formula (2): ${\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_t}^{\left(l\right)}\right)={\mathrm{\σ}}^2\left({{\mathrm{\ϵ}}_{t+s}}^{\left(l\right)}\right)=\frac{1}{N}{\mathrm{\σ}}^2---\left(4\right)$

So, sequence { ε _t ^(l)S item correlation coefficient ρ _{T, t+s}For:

${\mathrm{\ρ}}_{t,t+s}=\left\{\begin{array}{cc}\frac{N-s}{N}& (N>s)\\ 0& (N\≤s)\end{array}\right.---\left(5\right)$

Can know sequence { ε by formula (5) _t ^(l)Adjacent s item have positive correlation coefficient, promptly original incoherent random sequence { ε _tHave positive correlation through after the rolling average, and make the random fluctuation sequence of non-rule become smooth fluctuation sequence.

4. pitch control method is proofreaied and correct in the forecast of double-fed induction wind-powered electricity generation unit according to claim 1, it is characterized in that: in step 2, wind speed is got optimum propeller pitch angle β during less than rated wind speed _OptAs becoming oar control propeller pitch angle predicted value, said optimum propeller pitch angle β _OptObtain through the foline momentum method.

5. pitch control method is proofreaied and correct in the forecast of double-fed induction wind-powered electricity generation unit according to claim 1, it is characterized in that: in step 2, wind speed obtains the propeller pitch angle predicted value under the current air speed value through the Newton interpolation during greater than rated wind speed.

6. proofread and correct pitch control method according to the forecast of claim 1,4 or 5 described double-fed induction wind-powered electricity generation units, it is characterized in that: in step 2, confirm propeller pitch angle β predicted value through following arbitrary method, wherein:

When 2-1) wind speed was less than rated wind speed, there was different optimum propeller pitch angle β in different wind _Opt, can know the mechanical output P that wind turbine produces according to aerodynamic principle _TurFor:

$P_{\mathrm{tur}}=\frac{1}{2}\mathrm{\ρ\π}{R}^2{C}_p(\mathrm{\λ},\mathrm{\β})V_W^3---\left(6\right)$

In the formula (6): ρ is an air density, and R is the wind wheel radius, V _WFor driving the effective wind speed of wind turbine, tip speed ratio λ=w _TurR/V _W, w _TurBe wind speed round, C _pBe the wind wheel utilization factor, according to the function C of curve fitting _pFor:

$\left\{\begin{array}{c}{C}_p(\mathrm{\λ},\mathrm{\β})=0.22(\frac{116}{{\mathrm{\λ}}_i}-0.4\mathrm{\β}-5.0)e^{\frac{-12.5}{{\mathrm{\λ}}_i}}\\ {\mathrm{\λ}}_i=\frac{1}{\frac{1}{\mathrm{\λ}+0.08\mathrm{\β}}-\frac{0.035}{{\mathrm{\β}}^2+1}}\end{array}\right.---\left(7\right)$

When 2-2) wind speed is greater than rated wind speed, the permanent rotating speed operation of wind-driven generator this moment, the wind-driven generator output power is a rated power; Wind turbine rotating speed and output power are can the knowledge amount, simultaneously, because wind turbine blade radius is a definite value; Air density can be considered constant; Then variable blade control system will change and move with wind speed, and the propeller pitch angle output value can be determined by wind speed

Adopt Newton interpolation method match wind speed-propeller pitch angle change curve, n the Newton interpolation polynomial that is calculated wind speed-propeller pitch angle by formula (6), (7) is:

β′ _n(V _W)＝β[V _W0]+β[V _W0，V _W1](V _W-V _W0)+β[V _W0，V _W1，V _W2](V _W-V _W0)(V _W-V _W1)+…

+β[V _W0，V _W1，…，V _Wn](V _W-V _W0)(V _W-V _W1)…(V _W-V _W（n-1）)(9)

In the formula: β [V _W0, V _W1..., V _Wn] be n the n jump quotient that the corresponding propeller pitch angles of different wind speed calculate, by the pairing propeller pitch angle value of different wind speed β [V _W0], β [V _W1] ..., β [V _Wn] calculate:

7. pitch control method is proofreaied and correct in the forecast of double-fed induction wind-powered electricity generation unit according to claim 1, and it is characterized in that: in the said step 3, the step of the said propeller pitch angle β of drift correction predicted value is following:

3-1) input signal is wattful power messurement value and the rotating speed deviate that wind-driven generator sends, and obtains the propeller pitch angle reference value through PI control;

3-2) the propeller pitch angle reference value compares with actual propeller pitch angle, obtains servomechanism installation and servo ratio FACTOR P that the propeller pitch angle error signal is input to pitch control system _PitchMultiply each other.

8. pitch control method is proofreaied and correct in the forecast of double-fed induction wind-powered electricity generation unit according to claim 7, and it is characterized in that: said servomechanism installation is set to 0 ° and 27 ° respectively with propeller pitch angle β upper lower limit value, so that the safe and stable operation of said pitch control system.

Images